The constantly rising costs of material and labour in conjunction with building operations have led to an ever-increasing use of prefabricated units on building sites. Consequently an overwhelming proportion of the manual labor can be performed indoors, while the extent of the labor on the building site can be reduced. This leads to a rise in the quality of the completed building, since the bulk of the work takes place in an environment that is controlled with respect to wind and weather. These improvements in quality are especially noticeable in the use of constructional units that contain all walls or roof sections counted from the inside of the completed building to its outside. The present invention relates to a roof panel, which at least in certain embodiments is supplied to the building site in a completely finished condition, i.e. with both outer water-repellent roof cladding and completed inner roof cladding.